1. Field of the Invention
This invention relates to a high temperature surface combustion burner having a uniform surface combustion temperature and strong thermal shock resistance used for industrial furnaces and the like.
This invention further relates to a surface combustion burner having a wide combustion range and excellent durability.
2. Related Art Statements
Hitherto, as surface combustion burners, use has widely been made of a non-permeable ceramic plate provided with a number of throughholes, but said burner cannot be used in the field where uniform heating is required on the surface of ceramic plate, because the combustion takes place on the surface of the throughholes. As a result, the surface temperature of an intermediate portion between the throughholes is low, and it has further such shortcomings that the ceramic plate is liable to breakdown by thermal shock at the time of igniting the burner, because it takes time to make the surface of the ceramic plate, after ignition, become red hot. Thus, since thermal conductivity of the ceramic plate is high, when the surface combustion temperature is raised to more than 900.degree. C., the temperature in the vicinity of throughholes on the rear of the ceramic plate is raised to ignite fuel gas and to incur the danger of back fire, that notwithstanding the desirable surface temperature of more than 900.degree. C. in order to improve radiation efficiency, the surface temperature should be suppressed to less than about 900.degree. C.
As shown in Japanese Patent Laid-open No. 56-130,524, there is partially used a surface combustion burner for burning fuel gas on the surface of a metal fiber or ceramic fiber, but this surface combustion burner is advantageous because of its short amount of time between ignition to the red heat condition and easy processing however, it is disadvantageous for obtaining large radiation efficiency by raising the surface temperature owing to small corrosion resistance at high temperature.
On the other hand, as a prior surface combustion burner, a burner comprising a non-permeable ceramic plate provided with a number of throughholes is widely used, but in this type of burner, the combination is carried out on the surface of the throughholes only, so that the temperature distribution between portions where no throughholes exist, tends to be non-uniform, and the thermal conductivity of the ceramic plate is high, so that the temperature in the vicinity of the throughholes on the surface of the ceramic plate is raised to result in back fire, and in case of accelerating the injection speed of a mixed gas, a blow-off phenomenon is liable to occur, so that a high intensity combustion cannot be attained.
On the other hand, as shown in Japanese Utility Model Laid-open No. 60-6,933, a surface combustion burner with the use of a ceramic porous body having permeability has been known, which has a smaller problem of back fire due to small thermal conductivity, but this burner has such disadvantages that soot and dust formed from combustion clog the burner after operation for a long time to lower its permeability. Thus, the pressure loss rises, and combustion becomes non-uniform, and particularly, when using fuel such as coke oven gas containing more than 5 mg/Nm.sup.3 of soot and dust in fuel gas, LD gas, blast furnace gas, coal gasification gas and the like, the burner plate is clogged by soot and dust during combustion, so that this burner disadvantageously has a durability of only several hundred hours.